Blaise Pascal was born in Clermont on 19 June 1623 to a judge of the tax court, Etienne Pascal. By the age of eight Blaise had shown such promise that his father decided to move the family to Paris. Here Etienne could not only develop his own interest in mathematics but also ensure that Blaise met the finest intellects in France. Etienne had very modern views about education. He believed that a traditional education damaged the creativity of youth because of its emphasis on rote-learning texts and ideas ill matched to the interests of young people, however intelligent they were. Blaise was certainly intelligent, but his father forbade any formal teaching before the age of 12. He would then be taught languages, and only at the age of 16 would be allowed to study his father's main subject of interest, mathematics. He took the boy to visit his friends, and to his workplace, and encouraged the boy to ask questions on any subject. In addition he gave him lessons on a wide range of topics that he felt lay within a young boy's capacities and were likely to stimulate his imagination. But the attraction of the forbidden was too great.

Blaise wormed out of his father a definition of mathematics, which was 'the method of making correct figures and discovering the proportions which they bear to each other'. This was enough. When his father saw him one day drawing on sheets of paper and asked what he was doing the 12 year-old replied that he was trying to prove something about triangles.
It was Euclid's 32nd proposition, that the sum of the angles of a triangle is equal to two right angles. And he had succeeded. So Etienne gave in and let him have his copy of Euclid. At least that was what his adoring elder sister said. A less adoring witness said that the boy had already got himself a Euclid, and read it secretly.
By the age of 14 the boy was allowed to join the weekly meeting of the top French geometricians, such as Mersenne and Roberval, a group that eventually gave rise to the Acad?emie Franc?aise. At 16 he wrote a treatise on Conics good enough to make Descartes both jealous and suspicious that one so young could be so clever. Pascal's interest in tubes full of mercury arose from the sensational production of the first recorded vacuum. Galileo's last pupil, Evangelista Torricelli, took up his ideas for investigating why water pumps couldn't lift water higher than about 10 metres, but was more interested in his mathematical work than in physics experiments. So in 1643 he passed on the task of seeing how high a liquid column could maintain itself to the young Vincenzo Viviani. Viviani had been a pupil of Galileo's and stayed on to work with Torricelli. I suppose that the Health and Safety rules mean that nowadays teenagers never see this intriguing experiment, which is a pity .
It seemed logical to use mercury rather than water, and as mercury had fallen out but nothing had moved in, the length of tube above the mercury contained a vacuum. There was a problem though-what held the mercury column up? Torricelli believed that it was kept up by the weight of the air pushing down on the mercury in the bowl, and wrote to his friend M A Ricci that the aim of the experiment was 'not simply to produce a vacuum, but to make an instrument which shows the mutations of the air, now heavier and denser, and now lighter and thin'.
Torricelli's account of his experiment reached Mersenne in France in 1644, but couldn't be repeated because the necessary glass tubes were not available. Pascal heard about the Torricelli experiment in August 1646 and with some friends repeated it. They managed to get long enough tubes to carry out the experiment-some long enough to be used with wine (naturally enough) as the liquid, held up by being tied to the masts of a ship in Rouen harbour, where his father's job as a tax collector had taken the family.
Not everyone of scientific importance believed in the vacuum theory. In the Middle Ages Aristotle's ideas had become dogma. Even Ren?e Descartes thought that the top of the tube was full of 'subtle matter' that had somehow got into the tube via 'pores in the glass': for traditionalists the idea of a vacuum was simply unthinkable. Blaise Pascal moved to Paris in 1647 and in October published a small pamphlet Nouvelles Exp?eriences Touchant le Vide ('New Experiments about Emptiness'), describing his experiments at Rouen. The pamphlet created a stir, and Pascal became famous overnight. The clarity and rigour of his arguments and experiments were nearer to an Einsteinian than a 17th century scientific paper. For example, he pointed out that the space above the mercury was at least an 'apparent vacuum'. Also, it seemed to be empty of all the kinds of matter accessible to the senses, so maybe it is a genuine vacuum, however abhorrent to nature it might be.
Hence the remotely controlled experiment by his brother-in-law at Clermont. Pascal thought that Torricelli's idea of the mercury column being balanced by the weight of the air was correct. If the height of the mercury column was greater at the foot of the mountain than at the top, this would kill two birds with the same stone. The column was held up by the air, and 'Nobody could say that Nature has more abhorrence of a vacuum at the foot of a mountain than at the top of it ' . In this book Pascal developed a theory of pressure and not only explained clearly the basic physics underlying the Torricelli experiment but extended it to balancing liquid columns, essentially founding the science of hydrostatics.
Blaise Pascal was one of the most ingenious and interesting savants of the seventeenth century-and was by far the nicest. Down in Toulouse Pierre Fermat was condemning people to burning at the stake; in darkest Lincolnshire the posthumous child and mother-abandoned toddler Isaac Newton was incubating his neuroses. It was a time when Europe was torn by civil and religious wars. Cheerfulness was at a premium. In 1650 Pascal decided to give up science and mathematics to 'contemplate the greatness and misery of man'. He came back to science from time to time, inventing the hydraulic press, improving the calculating machine he had invented to help his father calculate taxes more quickly (nobody is perfect) and doing a lot more work in mathematics, especially geometry. The SI unit of pressure is the pascal (Pa).
But he is perhaps best known in France for his moral and religious works: the Letters to a Provincial and the Pens?ees ('Thoughts') helped to reform Catholic thinking even if some felt that they verged on the heretical. These books are still readily available in paperback. Pascal died in 1662 of a painful stomach cancer.